Japanese Patent Application Laid-open No. 2000-357757 (Patent Document 1) describes a structure in which two wiring substrates are connected via a contactor provided on a side face of a packaging board.
Japanese Patent Application Laid-open No. 2001-186778 (Patent Document 2) describes a power converter in which a substrate mounting a smoothing capacitor is stacked on a substrate mounting a switching element and the substrates are accommodated in a common case.